After the SIM card is installed in the phone, you can use the mobile network (Mobile web) to connect to the public network for Internet access.
Steps:
1. Please make sure that your phone is inserted into the SIM card and that the mobile data service has been activated.
2. Turn on mobile data
Method 1:
realme UI 3.0 and above versions: Settings > Mobile network >Turn on Mobile Data
realme UI 2.0 & 1.0: Settings > SIM card & mobile data > Mobile Data
realme UI R & Go & T & U & S Edition: Settings > Network & internet > Mobile network > Mobile Data
Method 2:
• Swipe down on the status bar from the top of the screen to turn on Mobile Data in Control Center
3. When the mobile network is turned on, the status bar signal icon is displayed 
(Data upstream and downstream flags), indicating that the phone is surfing the Internet through the mobile network
Related Articles:
How to do with slow mobile network
Unable to access the Internet with data network- How To Fix